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Abstract

To prevent oxidation of a Si surface after plasma etching step, a hydrogen based plasma treatment has been developed. In an example, an O2 strip is performed prior to a plasma treatment. Then, alkali wet etch is performed after each plasma treatment. Among various chemistry tests, we found that hydrogen-based treatment, e.g., a N2/H2 treatment, enables a Si mask to be removed by a wet etch process.

Copyright

Lam Research Corporation, May 2011

Country

United States

Language

English (United States)

This text was extracted from a PDF file.

This is the abbreviated version, containing approximately
45% of the total text.

Page 01 of 5

PLASMA HYDROGEN PASSIVATION FOR Si

MASK REMOVAL BY WET PROCESS

Authors:

Youn-Jin Oh,

Kenji Takeshita

and

Hitoshi Takahashi

Lam Research Corporation

ABSTRACT

To prevent oxidation of a Si surface after plasma etching step, a hydrogen based plasma treatment has been developed. In an example, an O2 strip is performed prior to a plasma treatment. Then, alkali wet etch is performed after each plasma treatment. Among various chemistry tests, we found that hydrogen-based treatment, e.g., a N2/H2 treatment, enables a Si mask to be removed by a wet etch process.

Page 02 of 5

BACKGROUND

[0001] As device features get smaller to 2x/1x nm generation, a Si hard mask becomes more popular because line wiggling and collapse are major issues when using an organic mask in a dielectric material etching method. However, a Si mask may remain after a dielectric etch, which is a challenging issue. To remove the remaining Si mask, a wet etch is performed. The additional wet etch may more preferably be performed as an ex-situ process, as opposed to an in-situ plasma process, because materials used in silicon etching chemistry such as Cl2,

NF3, and SF6 wears out silicon parts in the processing chamber. However, there is much difficulty when using a wet etching process, which generally uses an alkali based etchant, to remove a remaining Si mask. This will now be described with reference to FIGs. 1A-1B.

[0002]FIG. 1A is a cross-sectional view of an example wafer having a plurality of patterned layers.

(This page contains 00 pictures or other non-text object)

FIG. 1A

[0003] As illustrated in the figure, the wafer includes a substrate 100 and an oxide layer 104. A SiN stopper layer 102 is disposed between substrate 100 and oxide layer 104 to prevent diffusion between substrate 100 and oxide layer 104. A hard mask of amorphous silicon 106 is patterned on oxide layer 104.

[0004] An O2 stripping process is performed etch exposed portions of oxide layer 104 and SIN stopper layer 102. The oxygen in the O2 plasma reacts with the surface of amorphous silicon 106, as illustrated in FIG. 1B.

[0006] SiO2 layer 112 is resistant to an alkali wet etch process. Accordingly, once a Si mask surface is exposed to air, or is processed with an O2 strip, it is very difficult to etch out Si mask by alkali wet etch directly, as seen in FIG. 1D. In particular, even if an alkali wet etch process is performed, SiO2 layer 112 and amorphous silicon portions 110 remains.